Unfortunately, muting someone doesn't prevent that person from downvoting you. Let alone - from going through your blog and downvoting every single post and comment they find. And if the blooger's rep is lower than that of the downvoter - that could be devastating.

I wish muting would completely ban person from the blog (or that there would be a "block" or "ban" option in addition to "mute") but that unfortunately is not how it is :(